Taxonomically,theMolluscaofsouthernChilearemoderatelywellknown,buttheliteratureisscattered,thereis little information on their habitats, and distributional records are scarce for the Chilean archipelago lying between Isla Chiloe and Tierra del Fuego. In 1 998 a survey was made of the marine biodiversity of the Laguna San Rafael National Park and an area of the Chonos Archipelago immediately to the north (approximately 46° S). The Laguna consists of a basin of low salinity, strongly influenced by glacial meltwater, and the Estero Elefantes is a complex fjord system with both brackish and fully marine environments, including sheltered bays and exposed coasts. Collections of molluscs were made at 26 stations, from intertidal habitats, kelp plants and by dredging from depths of up to 15 m. A total of 62 species was recorded, consisting of 9 Polyplacophora, 33 Gastropoda and 20 Bivalvia. In order to facilitate future studies in the region, these are briefly described andall the shelled species illustrated ( 12 of these photographed for the first time). Notes are given on habitats, depth and salinity, and geographical ranges are reviewed. Biogeographically, the area lies at the poorly known southern extreme of the transitional zone between the Magellanic and Peruvian faunal provinces. As a result, 27% of the species records are extensions to the known ranges, representing northern limits of Magellanic forms and southern limits of Peruvian ones. Of the 62 species found, 48% could be classed as Magellanic (found in the transitional zone and southwards) and 8% as Peruvian (found in the transitional zone and northwards), while the remainder occurred in both provinces.